Business rules or game by the rules презентация

Business Rules
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Business rules — one of the main sources of functional requirements for software, they determine the capabilities that the system must have for the rules implementation.
! Karl Wiegers refers BR to non-functional requirements

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Business rule — defines or limits any aspects of the business;
Must — protect or control, or influence to operations of business structure
What is BR?

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Taxonomy

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Facts — the right statements about business.
Facts are also called invariants - invariable truths about the essence of data and their attributes. Business rules in many cases can refer to certain facts, but usually it is not translate directly into functional software requirements.
Examples:
Each computer has a unique inventory number;
Pay each order shipping;
from the cost of delivery, sales tax is not taken;
Record includes coordinates of an event;
Delivery time windows are 15 minutes, beginning on each quarter hour.
Facts

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Constraints — determine what operations the system and its users can perform.
Some constraints in BR:
must, can not, can not, only, etc.
Examples:
- a loan agreement for a person under 18 years old must be signed by one of his parents or a legal guardian;
a regular visitor of the library can postpone for himself up to 10 books;
commercial flight crews must rest every 24 hours for at least 8 hours;
Deliveries must be completed between 10:00am and 2:00pm local time.
All meals in a single order must be paid for using the same payment method.
Constraints

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The rule, under certain conditions leading to the implementation of any action, is called action enabler.
The rule can control some software functions, through which the application implements the desired behavior model when certain conditions are met.
The key rule structure «If < some condition is true or a certain event has occurred >, than < something will happen (action)»
Примеры:
If a record is outdated, it is moved to archive;
if the client ordered the book of the author who wrote several books, the client should be offered other books by this author before accepting the order;
Action Enablers

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Computers perform calculations, and therefore one of the classes of business rules defines computations performed using mathematical formulas and algorithms.
Примеры:
the unit price is reduced by 10% when ordering from 6 to 10 units, by 20% - when ordering from 11 to 20 units and by 30% - when ordering more than 20 units;
the total value of the order is calculated as the sum of the values of all ordered goods, minus the discounts on the amount, plus state and local taxes in the district where the goods will be delivered, plus the cost of delivery and plus an optional insurance fee.
Computations

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Inferences establishes new realities based on the certainty of certain conditions.
Inferences creates a new fact based on other facts or computations.
Inferences are often written in the "if-then" format, as action enabler; nevertheless, the section "then" of inference includes a fact or an assumption, and not an action.
Examples:
if the payment is not received within 30 calendar days from the date of sending the invoice, the account is overdue;
if the supplier can not deliver the ordered goods within five days of receipt of the order, the order is unfulfilled;
Inferences

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Template

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Example